Right now I have very less idea of how the recording works, so I will most probably stick to live play and record, like a basic piano cover; untill I get used to this task, multitrack recording won't be possible for me. So getting into the post, I need :
1. A USB type B to type A cable
2. USB OTG cable for Android
3. A voice recording compatible app
Otherwise
A laptop with Audacity app installed.
Does it mean that the onboard speakers of the instrument stops working while it is connected to any device through USB to Host port ?
If yes, then how could an app record and play audio at the same time, is that possible ? Because I want to do live playing, so it is mandatory for me to listen to the stuff I would be playing.
I'm not sure what an OTG cable is. What is that?
I do not think the speakers will stop playing when you're using the E453's audio-USB recording, but I am not sure because I've never tried it. I have a PSR-E433, which does not have built-in audio-USB. So, I use an external device that converts analog audio to USB data, and then hook that to the computer. The analog audio is coming from my keyboard's headphone jack, so when that is in use, yes, the speakers on my keyboard stop playing. However, the audio-USB device I'm using has an audio output so that I can hear what is being played from the computer and keyboard while I record additional tracks. If I just hook that audio output to an independent, dedicated amp and speaker system, then that is fine. But if it is routed through the same mixer/amp set-up that also is part of the audio chain providing the audio to the computer, then any tracks that I previously recorded get mixed in with the new track that I would now be recording, along with my keyboard playing for the new track, which I do not want to have happen.
Most DAW (digital audio workstation) apps can, indeed, record and play at the same time. That is the idea of "laying down tracks." You record one track, such as a bass line. Then, you go back and play the bass line track on the DAW, so that while you're listening to the bass line track you recorded, the app also allows you to record a new track of music, such as a piano melody track, to go long with the bass line. This allows you to build up a song with multiple parts of music that you do not have to play yourself at the same time, so that by the time you are done, it sounds like a whole band or orchestra is playing.
Your E453 has this capability built in, with its 6-track sequencer, and that is a great tool to get a multi-track song started. But it has limitations, such as the fact that if you make a mistake while playing, you have to re-record the entire track, not just the measure with the mistake. And the sequencer on the keyboard is not recording actual audio -- it is only recording the data for the notes you play, to tell the keyboard what notes and sounds to play when the song is played back (like a super-high-tech player piano). So, if your recording gets too complex, you can run out of polyphony and not all the notes will play back. But when the audio is sent to a DAW on the phone or computer, then the polyphony is not an issue, because now you're doing the recording on the DAW, not the keyboard's sequencer.
Since you said you just want to play "live" for now and not do multi-track recording, this will not be a concern for you initially. But over time, you may want to experiment with multi-track recording.
When you say a "voice recording compatible app", I assume you are talking about the app that would record music from the keyboard. I just point this out because, I imagine there are some very simple "voice recording" apps that would just simply record your voice through the phone's microphone (for recording voice memos, for example), and of course, you need something more capable than that. You need something that will record stereo audio through the USB port of your phone or computer.
If you use a laptop, keep in mind there are a variety of choices for DAW software, but yes, I use Audacity. I have not tried any other programs, however.