[Nexus 7 Q&A, Help & Troubleshooting] CiaobyDany:
Recovery bootloop?

I am new to the forum, I have read a lot of guides and rules and stuff like that and I know I shouldn't be posting, but with the search option, the only thing similar to my problem is this.

Which got no reply, probably because of lack of information, so I'll try to be as detailed as possible explaining my issue.

First of all, even though it's two years I'm installing custom ROMs for me and my friends, I'm not such an expert, all I ever did was reading guides and follow them step by step. I'm able to change ROM frequently, as long as I don't run into problems. Which is what happened.

So, I have the Nexus 7 2012 WiFi (grouper) since 2012. I kept stock firmware until one year ago, when Marshmallow got out and the devices didn't get an official update. After thinking on it a bit, I decided to install an unofficial version of CM13, following this thread:

http://xdaforums.com/nexus-7/development/rom-cyanogenmod-13-nexus-7-t3279938

I honestly don't remember which guide I used to install a recovery on my device, it was either one found here or probably the one posted on the Cyanogenmod site, since I distinctly recall it's name was Cyanogenmod recovery.

It all went smoothly and I enjoyed Marshmallow, until when Nougat came out and I found this.

http://xdaforums.com/nexus-7/orig-development/wip-linux-tegra-nv-3-4-bringup-t3128195

I decided I had to try it, since there were no other means for me to try the new OS (I didn't think about buying the Nexus 5X at the time).

The installation had some kind of problems, because I didn't manage to flash the new recovery, for some reasons and had the terrible idea to abort it by unplugging the device. However, it didn't seem to cause any problems, because I was able to boot in receovery (the Cyanogenmod one) and install the ROM. I wiped system and cache, installed the rom (and gapps, obviously) and when I turned on the device it strangely had all previous apps and manteined the same background image, making me think that it actually didn't wipe anything. Still, the rom was working and except a few bugs (phone and email apps continuously crashing which I had to disable right after the booting) there was nothing strange. Still, the ROM was definitely too slow (not that I'm accusing the devs, it was a great ROM, but there are hw limitations so that 1GB of RAM definitely is not enough for Nougat to run smoothly), and I decided to buy the Nexus 5X on which I could play as long as I wanted to with Nougat, so I decided to go back on the unofficial CM13. I downloaded the rom and the gapps, turned off the device, and my intention was to install them directly with the recovery, without using the pc. I first turned it on in the download mode because I never remember if the recovery/download mode are power+volume up/down, and then from the download mode I chose reboot in Recovery.

That's where mess happened. The Google logo with the opened locker appeared on the screen for a couple of seconds, then a split second of screen turned off, then another split second of the Google logo again and then the following loop:

For a split second I see the Android with its belly opened a red warning triangle sign and the writing "no command" below it.

Immediately after that, the image disappears and on the bottom of the screen I get the following message (with the three lines appearing one after the other, seemingly like a command line outputs):

Supprted API: 3

E:unknown fs_type "f2fs" for /cache

E:Can't mount /cache/recovery/last_locale

This message remains for some seconds, then the screen turns off and than it turns on again with the Android and so on.

I tried everything from connecting it to a PC, to pushing each kind of button (the only input which it seems to read is pushing for 8 seconds the power botton, which causes it to shut off, but when I release the button or I wait some other seconds, it will turn on again with the Google logo), but nothing works. The only way for it to stop is letting the battery die, since I cannot remove the battery. If I pug it to a PC it will charge, but when I try to turn it on, whichever button I push, I will be stuck with the loop.

In my (completely ignorant) opinion, there could have been issues with the recovery, which worked for unknown reasons when I installed the AOSP ROM and now is broken.

So, tl;dr: I have a bootloop in the recovery, I cannot turn it on, I cannot go in download mode and I obviously cannot use the recovery. Is there a way for me to flash something in it without having it turned on?

Sorry for the very long post, but I hope I have been as detailed as possible, and thanks in advance to everyone bothering to answer me or give me his 2 cents. As i said, I'm not experienced.