How to Install Newly Purchased Software on Quest 1 NOW

* 2025/3/14 updated : This issue seems solved for the time being. Anyway, I strongly recommend to back up apk & obb files of your purchased apps for Quest1 to prepare such kind of troubles.

Since the beginning of this month or so, It has been become unable to install software on the original Meta Quest (Oculus Quest 1).

Having had a terrible experience with the Oculus Go, I personally backed up all the Quest 1 software I had purchased so far using SideQuest. So, I am able to sideload and install software I bought in the past. However, for software I buy from now on that still supports Quest 1, I won't be able to install it on my Quest 1 even if I buy it.

After some trial and error, I succeeded in installing the software, so I'm leaving this as a memo.
This is a pretty tricky method (especially step 3 and 7 below), so I think it will be blocked and unusable at some point. (Usable as of March 8, 2025)
As a preliminary step, prepare a Quest 1 that can be connected to the PC version of SideQuest.

1. Create a new account separate from the account you are currently using. Create it as an adult account.
Hereinafter, the account you are currently using will be called "Current Account," and the new account will be called "New Account."
2. Add the New Account to the Quest 1 you are using with the Current Account and turn on "App Sharing."
3. Switch to the New Account and install the app from the New Account. (←For some reason, you can install the app with the New Account)
4. From SideQuest, install Apk Extractor to the New Account.
5. From the Unknown Apps section, launch Apk Extractor and create an backed up Apk of the installed app.
6. Connect the Quest to your PC and launch SideQuest.
7. From the Device Settings & Tools tab of SideQuest, turn on the Quest1's MTP mode.
8. Open the Quest's storage from Windows Explorer and copy the Apk file in the ExtractedApks folder to your PC.
9. For apps with OBB files, also copy the corresponding OBB file along with its folder from the Android\obb folder to your PC.

This completes the backup.
To install the app on the Current Account, sideload the back-uped APK file and, if necessary, copy the OBB file along with its folder to the Android\obb folder.