Nintendo has two forms of revision numbers that they use for their cartridge games. The first one is the "-n" identifier on the end of the serial number which means that something physical about the cartridge has changed. In 99% of the cases this is an update to the label.
Back in the mid-90's we saw a lot of "-1" games appear because common games that everyone wanted to buy were being distributed when the ESRB was being instituted. There are many games that have a standard version and a "-1" revision simply because the ESRB rating was slapped on the label.
Nintendo's own Player's Choice logo is another good example of many label updates that required a new revision number because of the addition of the Player's Choice badge.
What you are really interested in is the ROM version of the game that is on the memory chip on the PCB. For quality control Nintendo does mark their games with a ROM ID on the outside of the game. For any cartridge game with a label on the back (NES, SNES or N64) there is an impressed number on the sticker. For games with only a sticker on the front (GB, GBC, GBA) the number is impressed on the game label, with the exception of the DS and 3DS, which also have the revision stamped on the back.
This number represents the facility/manufacturing line that the cartridge was assembled on. If your cartridge has the first version of the original ROM you will only see the 2-digit facility number. However, if a new version of the ROM was released from the developer to manufacturing, then a letter was appended to the end of the facility code.
The first revision will be an "A", the second revision will be a "B", and so on. If you take a look at these identifiers you can determine which version of the ROM is on your cartridges. If both games have no revision code, or if they have the same revision code, choosing which game to keep is up to you.
The ROM version can be a bigger deal than the serial number variation, depending on the nature of the ROM change. Nintendo has been known to adjust the art in some of their games for no apparent reason. Choosing which revision is a matter of preference.
You may be wondering where to find out information about specific cartridge ROM variations. The best place to go for a detailed log of variations to game ROMs is The Cutting Room Floor. (Beware, this is a blackhole for retro-gamer nerds, such as myself!)
To be clear, this site DOES NOT distribute game ROM files but they have thoroughly documented differences between the software variations of many games, old and new, for Nintendo and many other systems.
The only unfortunate aspect of TCRF is that they do not claim which revision ID stamped on the game goes with which revision detailed on their site. Instead, they just say "Japanese Version 1" or "US Version 2" when outlining differences of ROM versions. You may have to read the details on specific revisions to determine which ones may exist on your cartridges but that's never a difficult process.
After you finish an up B move and enter the "helpless" falling state, you can fall through soft platforms by simply holding down on the joystick. This state is the only time you can fall through a platform as if it were not there.
Not all characters can do this. Examples include Kirby (the final down-stroke of his final cutter up B does not ever finish until interrupted by landing/getting hit/blast zone) as well as both Jigglypuff and Yoshi (the two non-jumping up B's). Also Falcon's up B does not make him helpless if it connects with an opponent (but does remove his second (aerial) jump). A related special case is Fox's up B (the fire fox) can also pass through soft platforms during the move itself, when aimed downwards.
In all other cases, you can't fall through a platform per se, so it must be done in two steps: land, then drop through. Given enough practice with the timing, it is possible to perform the two step sequence fluidly and almost seamlessly. The fastest way to drop through a platform from a standing state is to "shield drop" by pressing Z and down on the stick at the same time. It saves a frame or two of ducking animation compared to the normal smash the stick downwards method, and also works while running/dashing.
Best Answer
I've your battery is replaced and fully charged then the issue is most likely that the circuit which feeds that ROM chip isn't getting sufficient power.
I would look into replacing the capacitors on the board. Think there's only one or two.