Do I need a National Pokedex to get Rotom in Diamond version?

Go to the app store for your device and do a search on Facebook Messenger. Click on Facebook Messenger; if there are updates available, there will be an Update button...

If the person that made the car made it mobile-friendly, yes. If he didn't, you may have a hard time driving the car or you may not be able to...

Yes, nothing is wrong. Continue to work toward your goal and be patient.

You cannot catch a wild Rotom in Pokemon Sun or Moon. It must be traded through the Pokemon Bank from another game.

Yes. In Launch4j, under the JRE tab, it's the first field at the top.

When you say "very first version", I think you mean first playable version. Yes, you can change it to the fist playable versions by clicking on "enable Alpha" or "enable...

You can get a mate in the trial version, you just have to have 800+ experience. It's the same as in the full version. You do need the full version...

Nope. Sorry, but most one-time Pokemon (such as Rotom, Heatran, and the Lake Guardians) will never show back up again if you accidentally knock them out. Newer games do address...

Yes. If you have a lot of time to spare and have quick hands, considering you'll have to do a lot of trying and reseting before catching one.

Try another version of MCEdit. Maybe MCEdit couldn't locate the Minecraft folder which is why it said you need to download Minecraft.