Need a new Start - WD My Book World Edition II

Hi Experts… i really need some detailed help here…
I took a 10 year old device from my uncle… i was able to update a firmware to 01.02.14… and i can see the drive on windows computer network…i can access the admin page too… but as this is too old, and WD has stopped supporting, i was wondering how i can make the best use of this… What i really need help with is -
1 - Can i install a simple 3rd party firmware tht would make it good to use with the features for current time?
1- Wht softwares with a file browser like interface i can use this for windows 10 and mac to access the files in the folder?
2- how do i setup the back up system? With what apps? i tried good sync, doesnt work too well.
3 most importantly how do i access it from an external network? None of the wd apps seem to work…
4 how do i access from iphone??
Guys i know it is a 10 yr old device… but i m sure i can find ways to make the most of it?
Point 3 and 4 are most important. The app listed in the admin page for external access is not supported any more… what 3rd party apps ca i use for backup, and external access?
i m not really a computer expert, but i can follow instructions pretty well :-) Also port forwarding could be an issue, but with some hand holding ..may be i can… i have this attchd thru LAN to a Netgear ORBI.
Thanks in advance for all the help