You have a blockage in your main sewerline.
You have a problem with your venting system. This is why some codes now require a vent within 6" of the toilet. If you will add a vvent to your main line at the toilet you will stop this. Check to make sure your vents are not clogged by a bird or bees nest first.
What you probably need to do is snake out the vents. You probably have debris in them.1- you may have a slight blockage2- Poor venting and water Jetting will scour the piping rather then rodding
If there is a loud noise coming from the upstairs toilet when it is flushed, it could be a sign of a plumbing issue like a clog or a problem with the water pressure. It is best to contact a plumber to inspect and fix the problem to prevent any further damage.
partially clogged drain or vent, improperly installed vent or drain
As water drains, it displaces air in the pipes. If the vent or vents in your house are clogged up, the air must find another way out, which could be another drain in your house.
When a toilet bubbles when flushed, it is usually due to a blockage in the plumbing system. The blockage causes air to get trapped in the pipes, leading to the bubbling effect when the toilet is flushed.
When a toilet burps when flushed, it is usually due to air trapped in the plumbing system being released. This can happen if there is a blockage or restriction in the pipes, causing air to get trapped and then released when the toilet is flushed.
I do not know if popcorn can be flushed down the toilet. So, I wouldn't try it.- Ashton Smith
Yes you can flush it. It's possible for a toilet trap to go dry after that much time. When you flush just make sure you check to see if the bowl is leaking.
Toilet bubbles appear when flushed because of air trapped in the pipes or a partial blockage in the drain. This can happen even if the toilet is not fully clogged.
The sewer
Your toilet may be leaking from the bottom when flushed due to a damaged wax ring seal or a cracked toilet base. This can cause water to seep out when the toilet is flushed. It is important to address this issue promptly to prevent further damage and water wastage.
First thing you should do is call a plumber. Drain lines are not supposed to leak. Your drain line is clogged and needs to be snaked out and the leaking pipe repaired.