He can. You are just not watching or researching properly.
yes gohan can turn super sayian 1 actually gohan can even turn super saiyan 2
He Turned Super Saiyan back in his time when he found Future Gohan Dead.
gohan was the first one to turn super sayain two
gohan turns super saiyan 2 in episode number #170 It's actually DBZ Episode 185-Awakening
Perhaps. As said in Dragonball Gt, in order to turn to a super saiyan 4, the saiyan needed the proper physical condition (Power level Most likely around super saiyan 3 level) then receives causing the transformation to a golden great ape which the saiyan must find himself in the beast to transform to a super saiyan 4. And since gohan is stronger than a super saiyan 3 in mystic (Ultimate gohan) mode, he may turn into a super saiyan 4 However due to the fact he is a half saiyan he may not transform (Although this is not confirmed) Once again, however he did turn into a great ape in the saiyan saga in Dragon ball z so with his major power as ultimate gohan, he should turn into a golden great ape and then to a super saiyan 4.
Yes
Z
there is no super saiyan 8 only SSJ1, SSJ2. SSJ3, and SSJ4 but there is never a super saiyan 8 and I highly doubt there will be one until maybe in the later future...
when cell killed andriod 16 gohan got mad saying he wont wacth this any more.
Gohan is way stronger. he defeated cell when he was a child and goku couldn't as an adult. after losing to cell Goku even admits that Gohan is stronger than he is. it is not about who can turn into level 2 or 3 super saiyan it is about who is the strongest. that's what the ? asks. Who is stronger. in this category Gohan clearly wins.
Trunks turns super saiyan because after witnessing his friend gohan killed in the streets knowing it was the work of androids 17 and 18 explodes his anger explodes and he becomes a super saiyan.
Here they are:Goku: Super Saiyan 1, 2, 3, and 4Vegeta: Super Saiyan 1, Ultra Super Saiyan(Ussj), Super Saiyan 2, and 4.Trunks: Super Saiyan 1, Ultra Super Saiyan(Ussj), and Super Saiyan 2.Gohan: Super Saiyan 1, and 2.(Though he has Ultimate Gohan form, it doesn't really count.Teen Gohan: Super Saiyan 1, and 2.Kid Gohan: He doesn't turn Super Saiyan yet.Goten: Super Saiyan 1.Broly: Legendary Super Saiyan.(The rest like 1, 2, or 3 are not shown in DBZ)Gogeta: Super Saiyan 1, and 4.Vegito: Super Vegito(Which I think counts.)