[Sony Xperia ZR] sashank:
Hi,

1. Yes, you will be able to root and unlock the bootloader.

2. This phone has very limited worldwide availability, so very limited dev support too. There are virtually no ROMs for this device save for CM by FXP. That's also why the Xperia ZR forum is under the 'Legacy & Low activity devices' forum.

3. For Android development (both apps & ROMs), the phone should be great. It's basically the same as Xperia Z except for some software changes. If you're learning development and you become good at it, you can contribute to the ZR development forum yourself.

4. I've just got my ZR and haven't put a SIM card in yet, so haven't checked the call volume, but Sony provides a lot of settings to tweak call volume in Settings -> Call settings.

5. Almost every new generation phone gets hot. Unlike PCs, there's no fan heatsink + thermal paste to quickly radiate the heat from the CPU. It has to dissipate from the back of the device, and quad-core CPUs get quite hot during gaming and other CPU intensive tasks. Adding to that, the battery also generates some heat. So it's natural for a high end CPU bearing phone/tablet to get hot. That said, ZR heats up less than Xperia Z from what I know, both having the same processor. I'm guessing this is because of the thicker back on ZR. HTC One, Nexus 4, Samsung Galaxy S4, Nexus 7 all heat up so it's not a deal breaker.

TL;DR -

Custom ROM support - Don't buy ZR, it doesn't have any save for one at the moment. Whether the situation will improve in future, I don't know, but it seems unlikely because of ZRs limited availability. I bought ZR for my dad because custom ROMs and stuff don't matter to him. Regarding upgrades, Sony has already promised to update ZR to 4.3, and they might also update it to the next version too. For that we'll have to wait and see.

Excluding ROM support, there's absolutely no reason not to buy ZR. Compared to Z, the smaller 4.55" 720p screen actually contributes to battery life as there's slightly less backlight area + the GPU has to power far less pixels than a 1080p screen (less that half the number), and the screen clarity is great because of the smaller size (greater pixel density than a 5" 720p screen for example). You really can't make out the difference between 720p and 1080p screens at the normal distance you hold your phone at while using it. Only if you look very, very closely. So the added battery life advantage is a bonus. The battery is also removable, so you can keep a spare with you to swap immediately if you ever need to do that, and even when the battery goes bad you can easily replace it with a new one yourself. This phone also has a higher water-proof rating, and feels very sturdy compared to the glass backed Xperia Z.

The only real disadvantages of the ZR compared to Z are the much lower resolution front facing camera (but then again most video calling apps don't do HD and therefore don't make use of a high-res camera), and 8GB internal storage instead of 16GB. That might be a problem if you install a lot of games and the phone doesn't allow to move them to a microSD card. I'm not sure if it allows that or not, so you'll have to check with others.

If you want ROM support, buy Nexus 4 or Xperia ZR. They have PLENTY of ROMs. If you don't care about that so much, you can't go wrong with this phone. You'll also get at least Android 4.3 officially by Sony, if not the next version too.

Hope that helped.