Q&A for How to Make a Dual Cobblestone Generator in Minecraft

Yes, just as long as it isn't flammable. Other stones you can use are bricks or sandstone.

Just make sure you straighten the water by adding more blocks or digging a hole.

Dirt is not flammable. Flammable blocks include wood, leaves, wool and beds, but not stone or dirt.

In an obsidian generator you would need lots of sources of lava and you would continuously need to place more whenever the blocks are created.

A dual cobble generator is unique because it lets you mine cobble more slowly. Another idea to make the cobble generator more unique is if you have a redstone clock that powers a piston, which would push the cobble away for you to mine.

Yes, you could replace the stone blocks with TNT. Beware, though, that if you have a flammable block next to TNT, the block may light the TNT on fire.

Roblox does not have the same rules as Minecraft. You cannot generate cobblestone.

Yes, you can, just make sure the block you're using is NOT flammable. Blocks that will work include: sandstone, quartz, diamond, emerald, stone bricks, bricks, obsidian, and bedrock, just to name a few.

It is not. The only items that are flammable are wood-based blocks and wool-based blocks. This includes leaves.

Your lava turned to obsidian because water was poured onto the lava source block. When generating cobble, always make sure you water is touching lava that is flowing and not standing still. When water touches lava that is standing still, that lava will become obsidian.

Yes it will still work in the 1.13.2 model. Just give it a try and you'll see it works fine.