I own A1800. So,I'll try to answer your questions based on my experience in using the phone.
1. A1800 isn't a Linux or Magx or P2K. It's an ODM. So,don't expect too much to mod this phone.
2. I've tried everything to backup my data. But it's impossible as my A1800 can't connect to MPT.

3. The speaker isn't loud. It's just average. I don't have any issues with the sound.
4. The GPS won't work in another country except China.
6. It's a dual on GSM-CDMA. It works fine. The touchscreen really helps a lot in choosing which SIM do you want to use.
7. It doesn't support java. I heard that it just supports China Unicom Brew apps.
8. What did you mean? Is it lock application? A1800 has security option but there's no lock application. But you can Blacklist or Whitelist calls.
9. ODM and unmodded although I have collected some firmwares of A1800. I haven't flashed it yet. We need RSD CDMA to flash this phone. My firmware is 58.03.29.00.
My A1800 is just for daily use. I put a 4GB SDHC card on my A1800 and it runs perfectly. It's faster than A1200. I have no issue with the speed. Too bad the GPS and java don't work. But the dual sim of GSM-CDMA is a great option outside those Chinese phones.