One-eyed williy is a fictionnal character but his story is inspired by the legend of the Santo Cristo de Burgos | Source
Yes it was ! They made a fanstastic ship at the Warner Bros Stage 16. The ship we see at the end is actually a model.

They shot the beginning sequences in Astoria, Oregon. The car race at Cannon Beach, the restaurant exterior at Ecola Park and the finale sequence at Goat Rock State Beach in Sonoma County, California. The interior of the house was really the house, only the attic was filmed in studio because the actual house attic was too small (and probably dangerous). The rest of the movie was shot at Warner Bros.
The house location is 38th St, 368, Astoria, Oregon, USA
More about the Goonies house on this page !
The house is a private property and visits are not allowed. During the past Goonies anniversary events it was possible to buy tickets to visit the house. Now the house has a new owner and I don’t know if it will be possible to visit or not.
The house has a website here !

They were not allowed to see the set before filming. Richard Donner wanted to see their surprise on screen but Corey Feldman told that a few of them saw the set before… true or not ?
A lot ! You can see some of them here :)
Otherwise, some scenes has been filmed but lost like the Data indimidator scene when he confronts the Fratelli on the boat with a gadget who didn’t work and we could see smoke from his jacket (you can see 3 photos on the Souvenir Magazine). The best is, to me, to read the novel. You’ll learn a lot of things !
I would say YES absolutely but, let’s be honest, the movie can be scary sometimes (like when we meet Sloth) and the language is not always very kids friendly.
They filmed the movie in the autumn of 1984 and they released it on june 7th - 1985 - in the USA | Source
The Omen, Superman and Lethal Weapon director Richard Donner,
Steven Spielberg also directed some sequences.
The main actors are Sean Astin (Mikey), Corey Feldman (Mouth), Jeff Cohen (Chunk), Ke Huy Quan (Data), Josh Brolin (Brand), Kerri Green (Andy), Martha Plimpton (Stef). The Fratellis actors are Anne Ramsey (Mama), Joe Pantoliano (Francis), Robert Davi (Jake) and John Matuszak (Sloth)
Sean Astin was 14, Corey Feldman was 13, Jeff Cohen was 11, Ke Huy Quan was 14, Jeff Brolin was 17, Kerri Green was 17, Martha Plimpton was 14

It’s an homage to director Richard Donner who directed the movie Superman (1978)
Probably « Goonies never say die ! » It means the Goonies never give up, even when things become difficult or dangerous. The phrase represents friendship, courage, determination, and loyalty — key themes throughout the film.
You can find more Goonies quotes at this page !
Dave Grusin composed this magical masterpiece. He released the soundtrack for the 25th anniversary.
Otherwise the main song of the Goonies is « Good Enough » by Cyndi Lauper.
Other songs in the movie are :
« Eight Arms to Hold You » (Goon Squad),
« Love Is Alive » (Philip Bailey),
« I Got Nothing » (Bangles),
« 14K » (Teena Marie)
« Wherever You're Goin’ » (REO Speedwagon)
« She's So Good to Me » (Luther Vandross)
« What a Thrill » (Cyndi Lauper)
« Save the Night » (Joseph Williams)
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The character of Dennis Nedry has a funny wardrobe :) He has a shirt similar to the one worn by Chunk… He also has a Members Only jacket similar to Mouth and he also has a yellow rain jacket like Mikey. Probably an homage from Steven Spielberg.
To be honest I don’t think so. They talk about making a sequel since 20+ years and nothing happened.
I’m not a big fan of sequels, reboots, remakes… I prefer if they let this movie alone.