Understanding the Verbs and Participles in Philippians 2:6-7

1. hegesato is the only verb in Philippians 2:6. 
2. hegesato is an aorist. Aorist refers to the action that occurred at an indefinite time in the past. Jesus did this (hegesato) action at an indefinite time in the past. 
3. The present participle huparchon [1] gives us an idea about in what state Jesus did the action of hegesato (e.g. Jesus ''thought'' about it while ''being'' in the form of God).
4.  In aorist verbs, we really don't know if the action continues to happen until the present time (imperfect aspect). In aorist, we only know that the action already occurred (perfect aspect). Aorist is indefinite and only the context can determine exactly when the action occurred.
5.  In the context of Philippians 2:6 (v. 7), we're told about another action (ekenosen) in the aorist. Jesus did empty himself at an indefinite time in the past. As to how Jesus did the self-emptying, Paul used two aorist participles (unlike the present particple in v. 6): labon ( have taken) and genomenos (have become). We still don't know when exactly these actions occurred since these participles are in the aorist.
6.  The prepositional phrases ''en homoiomati anthropon'' and ''en moprhe theou'' (in combination with the verbs occurred with them) showed us that Jesus was existing in God's form and then become in men's likeness. 
7. This showed us that Jesus had existed prior to becoming in the likeness of men. Hence, genomenos en homoiomati anthropon points us to the specific time of Christ's birth (c. 4 - 6 BCE). So the actions hegesato and ekenosen occurred before Christ's birth but there was no specific time exactly when (was the hegesato happened before time or before Abraham was born in 3000 BCE? John 8:58, or before the world was? John 17:5).

Notes

[1] Participles has no tense because it is not a finite verb.  A participle only looks like a verb (i.e. verbal). In English and Greek, there exists ''finite verbs'' (shows tense) and ''non-finite verbs'' (doesn't shows tense). I was speaking of the latter whilst you are speaking of the former. Hence, the misunderstandings. huparchon is not a verb that shows tense (non-finite verbs). The evidence for this is huparchon being a participle. Participle will never be a finite verb.

Note that it is impossible to refer to the scenario in Philippians 2:6 in the present time because the only verb there is in the indefinite past (aorist). Huparchon only refers to the state / condition when Jesus did the action of hegesato. 

Note that a participle can be translated into different tenses. The tense of a participle depends on the main verb found in the context. For example, In Philippians 2:6 it has ''present participle''. In v. 7 it had two ''aorist participles''. For example, huparchon could take the tense of the main verb (hegesato), and it would be past tense because hegesato was an aorist (referring to action happened at an indefinite time in the past). Ergo, we have ''was existing''.