I would not use this to support a chair with rollers; depending on the size of the pads on your particular chair the pads may leave dents in the face plies. Feet smaller than 3/4” each will concentrate the weight of the chair high enough that they will leave dents
Plywood used for an exterior door at some point will probably start to delaminate. If the door is protected from the elements it will have a better chance to perform as expected. Overall I would not recommend it for an exterior door
Yes. Don’t expect perfect cuts. They can’t be responsible for cabinet precision.
you would have to ask your local store if their cutting wood
They will do cuts free. Every cut after that is .50 or .75 cent.
Sheet goods, especially plywood, is like anything else, you get what you pay for. A lot of the plywood sold at big box stores is used as full sheets (decking, sub-floors etc), where some voids and thin-glued areas don't matter. I find that I have to pay a premium price to get premium plywood, which may not be available at the multi-department home improvement stores.
Perhaps. Under the correct conditions this 1/2 thick plywood material will be an excellent substrate for a countertop. 1) to make this material strong enough to take the abuse; glue two thicknesses together with Titebond-3 water-proof glue, using enough 3/4” screws on 6” centers to pull the 2 panels together while the glue is still tacky. From start to last screw driven you’ll have about 8 minutes open time between when you first start to apply the glue, spread it over one of the surfaces, clamp it together and drive the screws home , so it would be a good idea to predrill the holes for the ~20-25 screws you’ll need. 2) once you have a 1” thick plywood panel with birch veneers on the outside, if you’re planning on staining it to get the color or tint you want- this would be the time to do it. 3) sand the good side of the panel (the other side will have about 20-25 screws buried in its surface) thru the grit (120x, 180x, 240x) dampen the surface with water just once to raise the grain and sand it again quickly with the 240 grit. Let it completely dry. After staining, resand with 400 grit and then seal both sides with a good waterborne urethane finish like the General finishes brand (it’s not cheap) apply 2 coats on the screwed together side; apply 4 coats to the good side, following the directions on the can. 4) Now you’ve a panel that’s both strong enough and sealed. If you’ve decided to do a hardwood edge (to cover up the edges of the plies. Trim off 1/4” using a 60 tooth 10 “ carbide-tipped sawblade on your table saw. Make the cut is straight. Glue on (using Titebond 3 again) the hardwood edging - use white oak since it’s both hard, strong, and tolerates water pretty well, and it accepts glue. Attach it with 16 gauge pneumatically driven nails below the surface. Then seal it just like the plywood panels and it’ll work great for the next 15 years.
The Veneer is not thick enough. You’ll run into so many issues with making your own. We had to patch a floor once. We cut down another engineered floor and put tongue and groove. Didn’t work very well.