Your pocket bomb doesn't have any actual bomb in it (unless the Israelis put some there, like the Hezbollah pagers and walkie-talkies.) They can burn fast, but afaik they don't explode, just like gunpowder doesn't explode. It burns very fast. On the other hand, they can produce gas and burst the battery pack, which might be considered an explosion, but I'd argue it's not actually one.

Which isn't going to make someone who has it happen in their pocket feel any better.

If I have my physics wrong, please correct me, I'm not a lithium bomb expert :)

does such battery really be this hazardous?

Only if the zionists added some grams of explosive material like they did with the pagers.

I thought they catch fire and burn down slowly.

Correct. Both the recent pager and radio attacks, and the 1996 cell phone attack, were performed by planting military explosives inside the devices in advance.

There is no magical way to hack the electronics to make a lithium battery straight up explode.

The cylindrical lithium cells can go off like a rocket, but the pouch cells in a phone just burn and are very difficult to extinguish.

Apart from the Galaxy Note 7 which had a design flaw in the battery, it's incredibly rare for a phone battery to catch fire without physical damage though.