three questions about my 4 wheel drive on '94 gmc

[Reaper69689]

I have a 94 Gmc Sierra 4x4 used it 2 or three times since I bought it but like all of u it delays in the 4x4 engagement but I don't know how long it takes and don't feel it engage I pulled out a jacked up newer 4x4 the other day put mine in 4 low and when I was pullingin reverse no tire was spinning but after tugging back and fourth 4x4 engage and front tire started spinning and got him out but not the frist time like this its happen but grinds when changing it from 4L to 4h or from either one back to 2 high and whole time truck is in neutral does it do this cuz I'm in neutral can I engage and or disengage while in drive??