You’re cooking them to death. Lower heat, add some water, cover with a lid to steam them. If you want a slightly blackened outside, do the above then take them out, raise the heat, and braze them quickly so they don’t dry out.

Depends on the dish. If it’s a separate side dish, I generally put it in a pot with a small amount of water and boil them for a few minutes, drain and then toss in a bowl and season.

If it’s in a dish with sauce, (think something along the lines of a brown gravy, or a curry, etc) I’ll throw them directly in near the end as to not overcook.

I microwave them and add them to something tasty like a sauce or curry to conceal them.

You can rinse them in warm water first and let them drain for a while. Or you can add more sauce to your stir fry as you cook, ie soy sauce, or whatever you are using.

Boil them. 1/2 cup water per 1 cup veggies.

Steaming works, too. Add less water, cover, simmer well.

Season them, too. Salt, garlic powder, onion powder and some MSG go a long way with bland frozen veggies.