In reverse chronological order.
The dots mark important steps in the development process. The more dots, the closer to the finished system.
Development
WordPress database error: [Expression #25 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'vertel_blog.wp_post2cat.rel_id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by]
SELECT DISTINCT * FROM wp_posts , wp_post2cat WHERE post_date <= '2021-03-01 12:04:37' AND (post_status = 'publish') AND wp_posts.ID = wp_post2cat.post_id AND wp_post2cat.category_id = 1 GROUP BY wp_posts.ID ORDER BY post_date DESC LIMIT 0,9999
WordPress database error: [Expression #25 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'vertel_blog.wp_post2cat.rel_id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by]
SELECT DISTINCT * FROM wp_posts , wp_post2cat WHERE post_date <= '2021-03-01 12:04:37' AND (post_status = 'publish') AND wp_posts.ID = wp_post2cat.post_id AND wp_post2cat.category_id = 2 GROUP BY wp_posts.ID ORDER BY post_date DESC LIMIT 0,9999
WordPress database error: [Expression #25 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'vertel_blog.wp_post2cat.rel_id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by]
SELECT DISTINCT * FROM wp_posts , wp_post2cat WHERE post_date <= '2021-03-01 12:04:37' AND (post_status = 'publish') AND wp_posts.ID = wp_post2cat.post_id AND wp_post2cat.category_id = 4 GROUP BY wp_posts.ID ORDER BY post_date DESC LIMIT 0,9999
WordPress database error: [Expression #25 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'vertel_blog.wp_post2cat.rel_id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by]
SELECT DISTINCT * FROM wp_posts , wp_post2cat WHERE post_date <= '2021-03-01 12:04:37' AND (post_status = 'publish') AND wp_posts.ID = wp_post2cat.post_id AND wp_post2cat.category_id = 5 GROUP BY wp_posts.ID ORDER BY post_date DESC LIMIT 0,9999
WordPress database error: [Expression #25 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'vertel_blog.wp_post2cat.rel_id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by]
SELECT DISTINCT * FROM wp_posts , wp_post2cat WHERE post_date <= '2021-03-01 12:04:37' AND (post_status = 'publish') AND wp_posts.ID = wp_post2cat.post_id AND wp_post2cat.category_id = 6 GROUP BY wp_posts.ID ORDER BY post_date DESC LIMIT 0,9999