Retin A (Tretinoin) helps with hyperpigmentation and acne so it is a good choice.
For hyperpigmentation, buy a 0.5 mm regular dermaroller and roll up to three times a week.
The raised scar next to the nose: Stamp it with a 1.5 mm dermastamp and right after stamping, perform the pressure massage. Apply pressure with your fingers onto the scar spot by spot. Apply pressure to each spot quite strongly for about 20 seconds. Repeat several times.
For acne scars, buy a 1.5 mm dermastamp with 35 needles. Preferably, combine the dermastamp with a 1.5 mm dermaroller.
It is better to stamp just a part of your face but thoroughly and densely.
Stamp the scars on one cheek (or half of the cheek), when it heals, stamp the other, when it heals stamp the forehead scars etc.
If the scars are not improving, try longer needles, apply Tretinoin cream right after stamping and use the suction pump.
The bumps on your forehead look like they might be seborrheic keratosis (seborrheic verruca) but it is difficult to say and I am not sure. Look it up in on the Internet. If it is, microneedling will not help but you can have it shaved it off or have cryotherapy.
How the skin reacts after microneedling and how quickly it heals is individual and there is no other way than doing a test patch on a very small part of your face. If you stamp on Friday evening, it should be OK on Monday morning. The suction pump may case bruising so again, you have to try it.
You should do the TCA prior to stamping. When it heals, start with microneedling.
To prevent hyperpigmentation, you must avoid sun exposure after mcironeedling as much as you can and apply a high factor sun protection. If you are however really very prone to hyperpigmentation after even small injuries such as bug bites etc. you may end up with hyperpigmentation after stamping. It is rare and it will disappear but do a test patch. Redness post-microneedling is normal.
Concerning the pores, I will paste here the relevant part from our dermarolling instructions:
Dermarolling works very effectively on acne scars but pores are not scars. Pores are ducts in the skin and their size is genetically determined. There is currently no method that can reliably and permanently make pores smaller. Very few of our customers managed to make their pores smaller through microneedling. You can try a regular 0.2 mm or a 0.5 dermaroller to thicken the epidermis or a 0.5 mm dermastamp. A thickened epidermis could make pores look smaller because the pore size is the smallest on the skin's surface and as you go deeper into the skin, the pore channel widens. Some of our customers improved their pore size with the single needle but always try just one pore to see if it is not making it worse. Do not expect results too soon.