Question on szlachta clan admission

As it is written in many researches untill the first half of 17 century szlachta clans could admit new members.
Can anybody explain:
1. Was such admission possible in case of a non-szlachtic before man?
2. Did such admission require King and Sejm confirmation or the mere fact of admission was sifficient for nobilitation?
3. I read nothing about clan structures, about any clan organization in post-knight period (since 16 century). Did clans really have organization? What were the structure and ways to elect major clan representatives?
4. Were the clans common with Lithania as in Crown?

Topic attached on merging:
Question on Uniate szlachta

I guess such question is more convenient for some forums in Belarus or West Ukraine but such question is unfortunately nearly unknown for example in Belarus today.
By chance, maybe somebody knows here...

As far as I know there were nearly no magnate Uniate families exept count Szepticki family. Is thet truth. Are some magnate families known that were Uniate and later became Roman Catholic?
In Belarus (Assembly of Belorussian szlachta) I was told that among little szlachta the percentage was in Litwa approximately equal to 30 percent? But no correspondent names were mentioned. Are such families known?
It is well known that Uniate clergy was from szlachta. But a detailed information is aslo unknown by me

No idea. I like history but don't know such detail.