Allow access to profile to only followers.

yzc_allow_profile_access_to_followers_only.php

<?php

/**
 * Allow access to profile to only followers.
 */
function yzc_allow_profile_access_to_followers_only() {
    if ( bp_is_user() ) {
        
    // Get Redirect URL.
    $redirect_url = home_url();

    if ( ! is_user_logged_in() ) {
        wp_redirect( $redirect_url );
        exit();
    }

    if ( bp_is_my_profile() || current_user_can( 'administrator' ) ) {
        return;
    }

    if ( ! bp_follow_is_following( array( 'leader_id' => bp_displayed_user_id(), 'follower_id' => bp_loggedin_user_id() ) ) ) {
        wp_redirect( $redirect_url );
        exit();
    }
    }
}

add_action( 'template_redirect', 'yzc_allow_profile_access_to_followers_only' );