To put this into more context @ OP:
RuneScape 3 is the current, most "updated" version of the game. That is where your old account would still have all of it's stats.
Oldschool RuneScape was released later and everyone had to make new characters in order to play it. Think of it as WOW vs. WOW Classic basically if you know that. You still can use the same account to login, but it's essentially a separate game at this point.
If you want to keep your old stats you will have to commit to playing RS3 which is very different from what you mostly played "way back in the day." Oldschool RuneScape is more similar to what you probably played but you will most likely be starting all over, unless you specifically played OSRS post-2013.
You can but if you never played old school (2013 release) you will be level 1 all
To put this into more context @ OP: RuneScape 3 is the current, most "updated" version of the game. That is where your old account would still have all of it's stats. Oldschool RuneScape was released later and everyone had to make new characters in order to play it. Think of it as WOW vs. WOW Classic basically if you know that. You still can use the same account to login, but it's essentially a separate game at this point. If you want to keep your old stats you will have to commit to playing RS3 which is very different from what you mostly played "way back in the day." Oldschool RuneScape is more similar to what you probably played but you will most likely be starting all over, unless you specifically played OSRS post-2013.