Not sure what engine you are working on but if you are using a new gasket there is no need for silicone unless the directions included with the new gasket require it.
Only in the corners.
You will need to remove the exhaust manifold retaining bolts in your 1993 Chevy Astro. Remove the exhaust manifold. Remove the exhaust manifold gasket and clean the surface. Reverse the process to install the new exhaust manifold gasket.
an exhaust flange gasket, is the gasket,commonly called a donut that is used to seal where the exhaust pipe is bolted to the exhaust manifold
No, You don't put anything on Head, Exahust or intake gaskets. CJ actually you do put a 1/8'th inch bead of black silicone on the gasket to ensure no leaks occur and it also helps hold the gasket in place when your putting the intake manifold on. I'm a ford master technician, you ALWAYS use silicone when replacing intake and head gaskets. =DK
You can make a paper gasket out of a cereal box that would be better than using Silicone -but if you can't figure that out use very little silicone.
Where is the leak coming from. Most likely you will need to replace the exhaust manifold gasket which will require removing the exhaust manifold.
You need a new Head Gasket.
Need to replace the valve cover gasket.
Sure. 100% silicone can be used. The sealant is not necessary as the gasket does the sealing anyway. the sealant does help hold the gasket in place for easier installation.
Yes, the exhaust manifold on a 99 Chevy S10 2.2 will need to be be removed during the blown head gasket repair.
gaskets exist to eliminate the need for adhesive, you do not need to glue them