Toilet Water Shoots upwards When Flushed like a volcano erupting
Water probably isn't "shooting upwards", but rather not draining fast enough based on the inflow of water.  Per your plumber, it is probably partially clogged.  With a toilet, you want to use a toilet auger instead of a snake as it is designed to get around the bend without damaging the finish of your toilet.

If you want to confirm its a draining issue, try pouring a bucket of water into the toilet. It should drain almost instantly without the level increasing.  If it doesn't, it's clogged.