Whats the difference between 変わらない and 代わらない? Both kanji have same meaning, so which one to use?

Thanks

So i gather in sentence form, いつも変わらない笑顔で and いつも代わらない笑顔で are both correct?

いつも変わらない笑顔で - your smiling face never change
いつも代わらない笑顔で - your smiling face is irreplaceable.

Anyone selling genki textbook? げんき教科書

Is there a Discord server created by Malaysians or any online session to practice speaking Japanese? I’ve joined a few EN-JP servers, but unfortunately, some seem to have members who aren't focused on language learning and instead engage in unrelated or inappropriate conversations.

I really need to pracitse 日本語会話. Any Lowyatians wanna speak in Japanese?　ぼろぼろ日本語だったら、大丈夫だと思うww