Question compilation

1- If Exeguttor uses grass moves, Scyther is better. And also Scyther can evolve in Scizor.

2- You are not right. Look their moveset

3. I don't know.

Extra: If it was 99% IV, I would say, transfer it... but it's 100%! It's up to you!

Hey! You don't transfer a 100% IV!
Make it an Exeggutor!
I'm guessing yours is only lvl 2.
Power it up to lvl 12 and you have the best trainer!
That won't cost you much...

Both Pinsir and Scyther will kill an Exeggutor about the same speed, because the 20 extra attack will probably not make a difference to how much damage is dealt due to the damage formula rounding down.

Scyther's flying typing will reduce Solar Beam and Seed Bomb damage, but most of your damage reduction will come from dodging, which reduces damage by 75%.

With Scyther, a dodge and double resistance to grass means you take 0.16x damage from grass moves (0.8 x 0.8 x 0.25 = 0.16).

With Pinsir, a dodge and single resistance to grass means you take 0.2x damage from grass moves (0.8 x 0.25 = 0.2), so you're still getting huge damage reductions. That small difference in resistance won't really be significant unless you're fighting multiple Exeggutor's in a row.

It's good for attackg fairys but they aren't that common in gyms anyway. As a defender they're decent too. Good CP and actually decent at defending (unlike a Gyarados for example). Good all round stats, the best defensive charge move is good against one of their counters (psychic types). Poison Jab is basically Zen Headbutt with poison typing, so it's a good defensive move.

It's biggest weakness is ground types though, since ground types deal extra damage to Muk and also resist poison, while psychic types only deal extra damage to Muk but don't resist poison, and Rhydon received one of the biggest buffs, so more people will be using them. But almost every Pokemon has a weakness anyway, and Golems / Rhydons are somewhat uncommon.

If Exeggcutes aren't that rare, then that one is probably worth evolving, because candies won't be rare for you. See if it's moveset is one you want, and if it is, then you can decide if you still want to power it up all the way. If the moveset isn't one you wanted, still keep it, because it might have value later on.

I can't attest to the viability of both Bug types vs. Exeggutor personally, but I do want to mention that you'll be more able to dodge Confusions and Zen Headbutts better with X-Scissor on Pinsir than Bug Buzz on Scyther. Bug Buzz's animation lasts so long that you'll almost guaranteed take a hit while doing it. This dodge difference may make up for Pinsir's lack of resistance to Grass.