Aphelion uses three small single-purpose block plugins, all free on WordPress.org. The demo import configures them for you; here’s what each one does in the theme:
The Icon Block adds a block for inline SVG icons. The theme uses it for the small interface icons — section markers, list bullets and the arrows on buttons. To change an icon, select the Icon block and pick a new icon or paste your own SVG.
Splide Carousel Block powers the sliders — the reviews carousel and any image carousels you build. Slides are regular blocks inside the carousel, so you edit them like any other content.
Dynamic Year Block renders the current year in the footer copyright line, so it never goes out of date.
Each plugin has its own documentation on WordPress.org if you want to go deeper.