Jesus' promise in John 5:24 NASB is conditioned on present believing, but you keep ignoring that without explaining why you do that.
OK, let's just get this over with and face the real meaning of the present tense, not the abuse that you've presented. Your explanation forces the present tense to be MUCH MORE than just current believing. You've forced it to mean to "keep on currently believing", which turns the present tense into some kind of other tense, which it is NOT.
You've taken a current action and forced it to mean on-going out into the future. So, please consult any Greek grammar text and determine whether the present tense EVER means that.
From Dan Wallace's Greek Grammar: Beyond the Basics, on p.514:
"With reference to aspect, the present tense is internal (that is, it portrays the action from inside of the event, without special regard for beginning or end), but it makes no comment as to fulfillment (or completion)."
This is why Jesus used the present tense in Luke 8:13 regarding the 2nd soil who 'believed for a while'. This PROVES that the present tense doesn't mean on-going in any sense.
So, until you're up to speed on the real meaning of the present tense, there is no use for any further discussion about it. I'm tired of having to keep on correcting your misunderstanding of it. It's pointless.
You leave me no choice but to conclude that Freegrace doctrine can not explain how Jesus says that it is he who "believes" (present tense) that has eternal life while it insists that is not necessary to believe (present tense) to have eternal life.
This is just flat wrong. The point of John 5:24 is about those who now (present tense) believe will not be judged, or condemned, but have passed from death to life.
This is no different than Jesus' promise that those He gives eternal life will never perish in Jn 10:28.
But, again, you're abusing the present tense.
"he who hears My word, and believes Him who sent Me, has eternal life, and does not come into judgment, but has passed out of death into life." (John 5:24 NASB bold)
You've mistranslated this verse to read thusly:
"he who hears My word, and
KEEPS ON BELIEVING Him who sent Me, has eternal life,
AND AS LONG AS HE KEEPS ON BELIEVING, will not come into judgment, and will pass out of death into life"
The red words in caps represents your faulty understanding of the present tense. It NEVER means that.
Your mistranslated reading includes conditional clauses that Jesus NEVER added.
There is no argument that a person receives eternal life the moment they believe.
That is the point of John 5:24. Thank you for noticing. And from that FACT, we understand from Jn 10:28 that those who have received eternal life will never perish. That's a direct and clear promise.
So, to never perish is the result of receiving eternal life.
The argument is that person, if they stop believing, does not satisfy Jesus' promise in John 5:24 NASB that it is "he who...believes (present tense) Him who sent Me has eternal lie" and, therefore, does not possess the eternal life they once had when they first believed.
This faulty conclusion is refuted directly by Jesus' promise in 10:28. To never perish is dependent ONLY ON receiving eternal life.
Your misunderstanding would lead to this rendition of John 10:28 -
I give them eternal life,
AND AS LONG AS THEY KEEP ON BELIEVING, they will never perish.
Again, the red words represent the faulty understanding of the present tense, and how one stays saved.
But Jesus made no such conditional statements. He was direct and blunt. He gives them eternal life and they will never perish. Eternal security.
They're not satisfying the additional requirement to be presently believing to have eternal life.
There are no "additional requirements" as you're doing. The verses are quite clear, but since you've totally misunderstood the present tense, you're not able to understand these verses properly.
You keep blowing off Jesus' own promise that it is the presently believing person that has eternal life and you keep bullying us with your unexplained insistence that the person who no longer presently believes has eternal life, which is completely contradictory to Jesus' own words.
This has been refuted repeatedly. And your faulty understanding of the present tense has been shown.
Jesus based His promise of never perishing on simply receiving eternal life in John 10:28. But your ideas add conditional clauses that are NOT in the Bible.
John 5:24 is not about those who KEEP ON BELIEVING. But those who currently believe, or believe NOW. There is NO suggestion from the present tense that they will KEEP ON BELIEVING. That is your own made up idea. It is NOT what the Greek present tense means.