accidentally added 2 cycle fuel into a 4 cycle tank?

Two cycle fuel is just gasoline with oil added. Shouldn't do more than fowl the plug as mentioned. Add more straight gas will dilute it. one tank of fuel shouldn't do any permanent damage. It will smoke while it burns it out.

Now cranking and starting are two different things. Cranking is turning over. Does the engine turn over when you hit the start button? If it does it is cranking. Not starting, the engine turns over but doesn't run. two different symptoms, different causes.

If it is not cranking, it is not the fuel. could be battery or starter or engine. If it is not starting, could be fouled plug or fuel filter. Pull the plugs, clean or replace it, set the gap and try again.

There probably isn't any physical damage to the engine, but possibly the spark plugs became fouled by carbon deposits. Cleaning and re-gapping, or replacing the plugs will remedy that.

As for the failure to crank,...Dead battery. Not related to the fuel problem, but rather to the charging system not doing its job.

Check the spark plugs; they are probably oil-fouled. If he only ran it for ten minutes, you're probably okay, otherwise. Continued running with oil in the fuel would carbon up the pistons and eventually you'd need to tear the engine apart.

No harm, just fouled the spark plug. Drain the carburetor and the fuel tank and refill with fresh gasoline. You may be able to get it started with the existing spark plug. Give it a try, it can't hurt. If it doesn't change the plug.

the 2 stroke fuel will do harm other than foul out the plug from too much oil on it.drain as much gas as you can drain the carb add fresh gas and you should be good to go.

cranking concern is likely not fuel related other than the spark plug fouled & excessive starter cranking may have burned up the starter or overheated the starter relay. check your fuses, check power supply to starter relay.

No damage. Just drain the tank & the carb's bowl. Clean or replace the sparkplug, as it's oil fowled.

it will not cause any damage at all. At most it made the spark plug a little dirty.

it probably doesnt start for some other reason.