We know that God does not change so to answer the question you must add one thing to another to gain the scheme of it. Take from the beginning, middle, and the end and see what is wise and have that to be your proven answer.
Let's begin.
Jeremiah 1:5
"Before I formed thee in the belly I knew thee; and before thou camest forth out
of the womb I sanctified thee, and I ordained thee a prophet unto the
nations"
Psalms 139 14-16
" I will praise thee; for I am fearfully and wonderfully made: marvellous are thy works; and that my soul knoweth right well. My substance was not hid from thee, when I was made in secret, and curiously wrought in the lowest parts of the earth. Thine eyes did see my substance, yet being unperfect; and in thy book all my members were written, which in continuance were fashioned, when as yet there was none of them."
Luke 10:19-20
"And the seventy returned again with joy, saying, Lord, even the devils are subject unto us through thy name. 18 And he said unto them, I beheld Satan as lightning fall from heaven. Behold, I give unto you power to tread on serpents and scorpions, and over all the power of the enemy: and nothing shall by any means hurt you. Notwithstanding in this rejoice not, that the spirits are subject unto you; but rather rejoice, because your names are written in heaven.
Psalms 69:28
"Let them be blotted out of the book of the living, and not be written with the
righteous."
Mark 10:35-40
"And James and John, the sons of Zebedee, come unto him, saying, Master, we would that thou shouldest do for us whatsoever we shall desire. And he said unto them, What would ye that I should do for you? They said unto him, Grant unto us that we may sit, one on thy right hand, and the other on thy left hand, in thy glory. But Jesus said unto them, Ye know not what ye ask: can ye drink of the cup that I drink of? and be baptized with the baptism that I am baptized with? And they said unto him, We can. And Jesus said unto them, Ye shall indeed drink of the cup that I drink of; and with the baptism that I am baptized withal shall ye be baptized: But to sit on my right hand and on my left hand is not mine to give; but it shall be given to them for whom it is prepared."
Matthew 20:20-23
Then came to him the mother of Zebedee's children with her sons, worshipping him, and desiring a certain thing of him. And he said unto her, What wilt thou? She saith unto him, Grant that these my two sons may sit, the one on thy right hand, and the other on the left, in thy kingdom. But Jesus answered and said, Ye know not what ye ask. Are ye able to drink of the cup that I shall drink of, and to be baptized with the baptism that I am baptized with? They say unto him, We are able. And he saith unto them, Ye shall drink indeed of my cup, and be baptized with the baptism that I am baptized with: but to sit on my right hand, and on my left, is not mine to give, but it shall be given to them for whom it is prepared of my Father.
Exodus 32:33
"And the LORD said unto Moses, Whosoever hath sinned against me, him will I blot
out of my book."
Revelation 3:5
"He that overcometh, the same shall be clothed in white raiment; and I will not
blot out his name out of the book of life, but I will confess his name before my
Father, and before his angels."
Now, see that you have the answer to two questions instead of one. First, understand that before any of us were born the Lord created us to be who we are and will be. Some He predestined to become like His son and others he predestined to become like Satan and his ilk. The names of the saints who have and will have salvation are written in a book before any of them were born. Thus the ledger is full and there are no empty spaces. So, look at what Christ said to the two and their mother "but to sit on my right hand, and on my left, is not mine to give, but it shall be given to them for whom it is prepared of my Father." So, those things that are already given in heaven shall not be taken and given to someone else. So, if the ledger is already filled with the names of those who shall be saved then it is vain to pray to God to save someone unto eternal salvation.
You are wasting your time and His time. Even if you begged Him He would not give salvation to those who He has not made for honor. So, no it is not scriptural to pray for salvation nor have you been commanded to do so. It is a wicked Father who gives his son's inheritance to a stranger and we know that God is righteous and never wicked.
The second question answered is the common one "Are we able to fall out of grace or to lose salvation". Here is the answer, all that God says is wise and therefore it is always true. You may also take the opposite of what He says and that is also always true. So, when God says:
"He that overcometh, the same shall be clothed in white raiment; and I will not
blot out his name out of the book of life, but I will confess his name before my
Father, and before his angels"
then you may say to yourself "He that DOES NOT overcometh, the same shall NOT be clothed in white rainment; and I WILL blot out his name out of the book of life, and I will NOT confess his name before my Father, and before His angels".
So, listen closely. Well was it said "For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, 5 And have tasted the good word of God, and the powers of the world to come, 6 If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame. 7 For the earth which drinketh in the rain that cometh oft upon it, and bringeth forth herbs meet for them by whom it is dressed, receiveth blessing from God: 8 But that which beareth thorns and briers is rejected, and is nigh unto cursing; whose end is to be burned."
So, it is possible for those who have received Christ and the Spirit to fall from grace unto eternal death. Ye, there is no condemnation IN Christ, but if you act outside of Christ which is rebellion, then you will be condemned to the same fate as the heathens for you shall have become as a heathen and God will blot out your name from the same book He wrote it in before you were born. Leaving not empty space where your name once was, but a mark so that none remember you.
I do hope this answers your question. There is lots more that has been said within scripture to prove both points, but I think this is sufficient.
You can also test both things.
You can try to make God do something He doesn't want to and see how that turns out.
You can forsake God and see how that turns out.
I recommend neither, but I recommend obedience and the forsaking of man's tradition because praying for salvation is now a common thing.
